DA-6 improves sunflower seed vigor under Al stress by regulating Al balance and ethylene metabolic.

Aluminum (Al) stress restricts plant seed germination and seedling growth seriously. Here, the sunflower "S175″ variety was used to explore the technique of improving seed vigor under Al stress and investigate the effect of diethyl aminoethyl hexanoate (DA-6) on physiological characteristics in sunflower seeds during germination under Al stress. The results showed that 3.0 mmol·L Al treatment significantly suppressed the sunflower seed germination and seedling growth. Al stress significantly increased Al content and secretion rates of citric and malic acids in sunflower seeds during germination. Besides, endogenous ethylene content was increased in Al-treated seeds. DA-6 serves as a positive signal to regulate the sunflower seed germination under Al stress. Moreover, DA-6 enhanced the activities of malic dehydrogenase, citrate synthase, and isocitrate dehydrogenase, up-regulated the expressions of organic acid transport-related genes (ALMT and MATE), resulting in reduced accumulation of Al. Furthermore, exogenous DA-6 mitigated excessive accumulation of ethylene by decreasing the 1-aminocyclopropane-1-dihydrodipicolinate synthase activity and related-gene expression. However, DA-6 treatment had no effect on abscisic acid or gibberellin metabolism in sunflower seeds under Al stress. These results confirmed that DA-6 application enhanced the germination capacity through induction of the synthesis and transport of malic and citric acids, and suppression of the excessive accumulation of endogenous ethylene, thus contributing to alleviate Al toxicity in sunflower seeds.